Radome for vehicles

ABSTRACT

It permits to implement decorative radomes in geometries where ink overlay is not suitable or it is not possible, e.g. in pieces with a high relief or great dimensions.

The present invention refers to a radome for protecting a radar devicewhile presenting a decorative metallic image, especially for radardevices disposed behind the front grill of an automobile.

BACKGROUND OF THE INVENTION

In general, radio transmitter-receiver devices, such as amillimeter-wave radar, have been employed as sensors for vehicularcollision avoidance and adaptive cruise control systems.

In a radar system or the like that measures obstacles in front of anautomobile and the distance between automobiles, the antenna waspreferably positioned in the center at the front of the vehicle toobtain maximum performance. Although the radar antenna could beinstalled near the front grill of automobile, it was preferable toconceal the antenna from view due to its non-aesthetic appearance and toshield the antenna from external environmental factors such as weatherand airborne contaminants.

In order to protect the antenna and avoid radio interference and signallosses of the radar device, it has been proposed to provide a radarwindow capable of transmitting radio waves in the front grillcorresponding where the radar antenna was located. This allowed radiowaves to pass in and out through the window. However, the radar windowdiminished the appearance of the front grill due to the interruption ofthe pattern of the grill structural elements. Further, unsightlyinternal portions of the vehicle, like the radar transmitter-receiver,could be seen through the radar window.

In U.S. Pat. No. 6,328,358 unity between the radar window and the frontgrill body was provided. The radar window as disclosed in U.S. Pat. No.6,328,358 was formed by laminating a plurality of resin layers formedwith concavity and convexity. This component provided an impression by ametal layer deposited with concavity and convexity between the resinlayers such that the fin member of the front grill appeared to extendacross the radar window without interruption.

Indium was used as a metal deposited in such radar window. Whendepositing indium on a deposit member, indium was not deposited on thesurface in a uniform film manner, but deposited in a nanometric insularmanner. In other words, when indium was deposited on the deposit member,the surface of the deposit member comprised a nanometric combination ofa deposit portion where indium was deposited in an insular manner and anon deposit portion where nothing was deposited.

In this case, radio waves could pass in and out through the non-depositportion and the surface of the deposit member could be recognized uponviewing as a member that had metallic luster, since the deposit portionhad indium deposited in a nanometric insular manner.

This selective way of deposition complicated the process of applicationof the indium metals. Further radio waves did not pass in and outsatisfactorily when the deposit portions were formed extremely closetogether. The conductivity of the metals required the use of low densityevaporation methods such as thermal evaporation. These methods did notguarantee a uniform deposition in thickness throughout the member orbetween members produced in the same batch. Other methods of depositionwould guarantee uniform insular deposition such sputtering, butsputtering provided a metal density that generates a high level ofattenuation, making the system useless for a radome application in frontof a radar antenna.

U.S. Pat. No. 6,328,358 discloses a thin metallic layer comprisingindium deposited on a metal portion area that could be viewed from theoutside at a plastic-plated member for the beam path of a radar device.However, it was necessary to ensure a bright design and the reliabilityof durability for radio transmittance by forming a stable protectivelayer so as not to allow the indium bright film layer to undergoexfoliation or be damaged by an external force, or to be corroded by anexternal environmental stress such as water or polluted air.

This was due to the following: indium is a very soft metallic materialwith a value of 1.2 in the Mohs hardness scale; indium corrodes underthe aforementioned environmental stress since it is basically a metallicmaterial; it is necessary to ensure the reliability of durability bysecuring the film thickness with certainty such that the bright-effectdesign of indium can be obtained without thickening the indium filmlayer more than is necessary, since a radio transmission loss occurs asa conductivity loss based on the fact that indium is basically ametallic material; and the indium layer melts due to the heat of moltenresin when successively conducting secondary formation of the liningresin on a resin-molded component in which a film is formed on thesurface of a base body in advance, since the melting point of indium is156° C., which is extremely low, for example.

Although indium film is suitable for a film of an emblem or the like asit shows a metallic color, it poses problems in that it readilyexperiences exfoliation and lacks durability and abrasion resistance.Also, indium film may corrode, since it is basically a metal. Thus, whena ceramic film comprising silicon dioxide is disposed, the durability isimproved and the film, or paint, can be protected. However, the ceramicfilm comprising silicon dioxide is colorless, so that the appearance ofa metallic color, for example, cannot be provided.

WO2012066417A1, in the name of the same applicant than the presentapplication, discloses a decorative radome comprising a substrate madeof a radio transmissive resin, a decoration layer comprising a pluralityof metalloid or metalloid alloy (Si, Ge) layers applied to the substrateproximal face, a radio transmissive resin overlying the decorationlayer, the resin overlying the decoration layer including a decorationink overlay. However, in practice it has be shown that this decorationink overlay is not suitable in pieces with a high relief or greatdimensions.

Therefore, the object of the present invention is to overcome theselimitations, providing other advantages that will be disclosedhereinafter.

SUMMARY OF THE INVENTION

The radome for vehicles according to the present invention comprises asubstrate formed of a radio transmissive resin, the substrate having aproximal face and a distal face and a decoration layer applied to theproximal face, the decoration layer comprising a metalloid or ametalloid alloy deposited on the surface of the proximal face, a firstradio transmissive resin layer partially overlying the decoration layer,and it is characterized in that it also comprises a second radiotransmissive resin layer overlying entirely the first radio transmissiveresin layer, including the areas of the decoration layer not overlaid bysaid first radio transmissive resin layer.

Preferably, said second radio transmissive resin layer is overmolded onsaid first radio transmissive resin layer.

Advantageously, said second radio transmissive resin layer covers only aportion of said first radio transmissive resin layer.

It must be pointed out that said metalloid or the metalloids of thealloy are selected from Silicon, Boron, Germanium, Arsenic, Antimonyand/or Tellurium.

According to possible embodiments, the decoration layer can alsocomprise at least one oxide.

The present invention also refers to a vehicle including a radome asdefined previously, including a front grill assembly, the radome beingpositioned within the grill assembly, the vehicle further including aradar antenna positioned behind and in registration with the radome.

With the radome according to the present invention, the followingadvantages can be provided:

-   -   It permits to implement decorative radomes in geometries where        ink overlay is not suitable or it is not possible, e.g. in        pieces with a high relief or great dimensions;    -   As both first and second resin layers are made from the same        material, their features are the same, and their adaptation is        very simple, with a minimum attenuation of the radar waves        crossing the radome;    -   As the material of both resin layers is the same, it is not        necessary to use indentations and cavities for joining them,        because their joint is just chemical and very robust.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary isometric view of a vehicle having a decorativeradome constructed in accordance with and embodying the inventionpositioned within a grill assembly and a radar antenna positioned behindthe radome;

FIG. 2 is a schematized sectional view through a portion of the radomepositioned within the grill and showing the radar antenna positionedwithin the vehicle behind the radome and with a detected object in frontof the vehicle, with a schematized representation of emitted andreflected radar waves; and

FIG. 3 is an isometric view of the radome showing a base layer, adecoration layer and a protective cover layer.

DESCRIPTION OF A PREFERRED EMBODIMENT

First of all, in the present specification and in the attached claims bythe term “metalloid” is meant any of the following compounds: Silicon,Boron, Germanium, Arsenic, Antimony and/or Tellurium.

Radomes cover microwave antennas to protect the antennas from rain, ice,wind and other environmental conditions and are also provided to concealthe antennas form view. A principal requirement is that the radome betransparent to radar or radio waves or provide but minimal signalattenuation and/or distortion.

The present invention relates to the use of a metalloid or metalloidalloy that can include one or more oxides for a radome. The presentinvention employs, for example, as a radome decoration layer, germaniumor silicon, that can be combined with an oxide, a metalloid of highelectric resistivity, i.e. 1 ohm m at 20° C.

Due to the high melting point of germanium 938.25° C. (or silicon 1414°C.) and its boiling point 2833° C. (3265° C. for silicon), this elementcannot be deposited using thermal evaporation methods like the onesapplied in the case of indium. Nevertheless, this constitutes anadvantage.

According to the present invention, Physical Vapor Deposition (PVD) orChemical Vapor Deposition (CVD) are the possible methods employed forthe deposition of metalloid and oxide layers over a substrate comprisinga base layer or body. Due to the deposition process of these techniques,uniformity of the decoration layer can be guaranteed.

The decorative radome for automotive vehicular applications of thepresent invention comprises a molded radome having a base layer or bodycomposed of a resin and a bright decoration layer on the surface of thebase layer or body, the bright decoration layer being composed of ametalloid, such as, germanium boron, silicon, arsenic, antimony ortellurium and/or a metalloid alloy that can be combined with one or moreoxides.

By using the layer of metalloid and/or metalloid alloy, and oxide, radiotransmittance can be improved by several orders of magnitude as comparedwith an indium layer or other metals such as, tin, as proposed in EP1560288 A2.

The high conductivity of metals like indium or tin, combined with thevariability of thickness of the deposition methods typically used,required each radar window to be tested for radar beam transmissivityduring the final stage of production. This increased dramatically themanufacturing cost of the radome.

With reference now in detail to the drawings, wherein like numerals willbe employed to denote like components throughout, as illustrated in FIG.1, the reference numeral 10 denotes generally a decorative radomeconstructed in accordance with and embodying the invention configuredfor mounting within a grill assembly 12 of a motor vehicle 14.

Positioned within the vehicle 14 behind and in registration with thedecorative radome 10 is a radar antenna 16.

FIG. 2 comprises a cross section of the radome 10 and illustrating thebeam path of a radar antenna according to the present invention.Preferably, a substrate comprising a layer or base body 18 having aproximal face and a distal face is molded of a transparent ornontransparent resin having low radio transmission loss or a resinresulting in low dielectric loss. On the surface of the proximal face, abright decoration layer 20 comprising metalloid and/or a metalloid alloythat can also include at least one oxide.

Pursuant to the invention, the decoration layer 20 is of uniformthickness. Ornamentation, such as a vehicle emblem, is provided byshaping the proximal face of the base layer or body 18 with projectingand or indented surface configurations.

The decorative radome 10 according to the present invention can furtherinclude a first nontransparent resin layer 22 which overlies thedecoration layer 20. Said first transmissive resin layer 22 may havesome openings through which the decoration layer 20 deposited on theproximal face of the base body 18 can be seen.

According to the invention, the decorative radome 10 also comprises asecond transparent radio transmissive resin layer 21 overlyingcompletely the first radio transmissive resin layer 22.

Depending on the geometry of the radome, said second radio transmissiveresin layer 21 can be overmolded on said first radio transmissive resinlayer 22, or said first radio transmissive resin layer 22 can beovermolded on said second radio transmissive resin layer 21. Radiotransmissive layer 22 may only partially cover the decoration layer 20deposited on the proximal face of the base body 18, while radiotransmissive resin 21 overlies completely radio transmissive resin 22,including any portion of the decoration layer 20 non covered by radiotransmissive resin 22.

The overlying of resin layers 21 and 22 over the base body 20 allows foradapting with ease the complete body to the mill metric wave semi wavelength, resulting in a lower attenuation for the radar waves.

The base layer or body 18, as well as resin layers 21 and 22, arecomposed of a material, that provides low radio transmission loss and issuperior in terms of dielectric properties. Relative permittivity E′ anddielectric loss tan δ, for example, provide an indication of thedielectric property.

As previously mentioned, the radar antenna 16 is mounted in anautomobile 14 and disposed behind the front grill assembly 12. Thedecorative radome 10, which includes a bright metallic emblem of anautomobile manufacturer or a specific decoration, is disposed within thefront grill assembly 12.

With reference to FIG. 2, it will be observed that millimeter waves 23from the radar device 16 are radiated forward through the radome 10 andreflection waves 24 from an object 26 return to the radar device 16through the radome 10.

The decorative layer 20 may be formed of a plurality of metalloid and/ormetalloid alloy and at least one oxide strata or alternating strata ofmetalloid and metalloid alloy with each strata having a thickness in theorder of 1 nm to 500 nm, and more preferably with a total thickness inthe order of 10 nm to 100 nm believed to be the most efficient inachieving the objectives of the present invention and for obtainingmetallic color effects.

Further the decorative layer may comprise alternating strata of onemetalloid and/or metalloid alloy and at least one oxide and strata ofanother metalloid.

Thus, it will be seen that there is provided a decorative radome forautomotive applications which achieves the various aspects, features andconsiderations of the present invention and which is well suited to meetthe conditions of practical usage.

Examples

A possible, non-limiting example of decoration on the proximal face ofthe substrate is a plurality of metalloid layers comprising Silicon andGermanium, and a plurality of oxide deposited layers from followingelements: Titanium (Ti), Vanadium (V), Chromium (Cr), Manganese (Mn),Zirconium (Zr), Niobium (Nb), Molybdenum (Mo), Hafnium (Hf), Tantalum(Ta), Tungsten (V), Iridium (Ir), Nickel (Ni), Platinum (Pt), Silver(Ag), Indium (In), Thallium (TI), Silicon (Si), Gallium (Ga) orAluminium (Al).

More preferably following layer combinations are suitable: Titaniumdioxide (TiO₂)+Silicon dioxide (SiO₂), Titanium dioxide (TiO₂)+Germaniumdioxide (GeO₂), Niobium pentoxide (Nb₂O₅)+Silicon dioxide (SiO₂),Niobium pentoxide (Nb₂O₅)+Germanium dioxide (GeO₂), Chromium oxide(Cr₂O₃)+Silicon dioxide (SiO₂), Chromium oxide (Cr₂O₃)+Germanium oxide(GeO₂), Hafnium oxide (HfO₂)+Silicon dioxide (SiO₂), Hafnium oxide(HfO₂)+Germanium dioxide (GeO₂), Zirconium dioxide (ZrO₂)+Silicondioxide (SiO₂), Zirconium dioxide (ZrO₂)+Germanium dioxide (GeO₂).

Since various possible embodiments might be made of the presentinvention and since various changes might be made in the exemplaryembodiment shown herein without departing from the spirit of theinvention, is to be understood that all matter herein described or shownin the accompanying drawings is to be interpreted as illustrative andnot in a limiting sense.

1. A radome for vehicles, comprising: a substrate formed of a radiotransmissive resin, the substrate having a proximal face and a distalface; a decoration layer applied to the proximal face, the decorationlayer comprising a metalloid or a metalloid alloy deposited on thesurface of the proximal face; and a first radio transmissive resin layerpartially overlying the decoration layer, wherein the radome alsocomprises a second radio transmissive resin layer overlying entirely thefirst radio transmissive resin layer, including the areas of thedecoration layer not overlaid by said first radio transmissive resinlayer.
 2. A radome for vehicles according to claim 1, wherein saidsecond radio transmissive resin layer is overmolded on said first radiotransmissive resin layer, or vice versa.
 3. A radome for vehiclesaccording to claim 1, wherein said first radio transmissive resin layercovers only a portion of said decoration layer.
 4. A radome for vehiclesaccording to claim 1, wherein said metalloid or the metalloids of thealloy are selected from Silicon, Boron, Germanium, Arsenic, Antimonyand/or Tellurium.
 5. A radome for vehicles according to claim 1, whereinthe decoration layer also comprises at least one oxide.
 6. Vehicleincluding a radome according to claim 1, including a front grillassembly, the radome being positioned within the grill assembly, thevehicle further including a radar antenna positioned behind and inregistration with the radome.